The invention relates to a multipole electrical switchgear apparatus, and in particular to a multipole switchgear apparatus comprising vacuum cartridges.
The document EP 0,346,603 describes a three-pole electrical switchgear apparatus comprising three identical polar breaking modules arranged side by side on a frame. Each module comprises a vacuum cartridge equipped with an operating rod movable in translation. A spring-loaded drive mechanism of known type comprising a pole shaft drives the operating rods of the three vacuum cartridges. Each operating rod is connected to the pole shaft by means of an independent connecting rod system proper to the corresponding breaking module. This connecting rod system is composed of a transmission lever arranged between two connecting rods, one of the connecting rods connecting the lever to a crank of the pole shaft and the other connecting rod connecting the lever to the operating rod of the vacuum cartridge. In practice, the vacuum cartridges of the different poles are liable to be subjected to different forces when either opening or closing takes place. When opening takes place, the contacts of a cartridge may be slightly welded, or on the contrary the electromagnetic forces induced by the currents on the contacts may tend to separate the contacts of one of the cartridges more violently. When closing takes place, in particular if it takes place on a short-circuit for one of the poles, one of the contacts may be subjected to very strong repulsion forces. On account of these different stresses on the rods of the vacuum cartridges of the different poles, the pole shaft is subjected to high torsion stresses, directly transmitted by the independent connecting rod systems of the different poles. There is then a risk of large dynamic torsional strain of the pole shaft, resulting in non-simultaneous closing or opening of the different cartridges. To counteract this risk, the pole shaft then has to be over-dimensioned so as to give it an additional torsional strength. Moreover, the switchgear apparatus does not enable the distance between the vacuum cartridges of the different poles to be easily varied. It is true that construction in identical and independent breaking modules would theoretically allow any arbitrary arrangement. However, a different pole shaft corresponds to each distance between poles, since the cranks of the pole shaft have to be spaced the same distance from one another as the cartridges. The pole shaft happens to be a particularly expensive part, all the more so as its torsional strength is critical. Furthermore, the necessity of providing different pole shafts for each distance between axes makes it impossible to design the mechanism as a functional unit pre-assembled in the plant independently from the breaking modules. The architecture hardly favors delayed differentiation of the different models of a switchgear apparatus range.
One object of the invention is to achieve a multipole electrical switchgear apparatus with independent polar breaking modules enabling simultaneous operation of the different modules. Another objective is to increase the modularity of a multipole switchgear apparatus with independent polar breaking modules, enabling the distance between poles to be changed at low cost. Another objective is to obtain an architecture enabling standardized functional sub-assemblies to be stocked and assembled at the last moment to meet the customer""s requirements.
According to the invention, these objectives are achieved by means of a multipole electrical switchgear apparatus comprising:
a support;
a drive mechanism equipped with a pole shaft rotating around a first geometric axis fixed with respect to the support;
a plurality of breaking modules, each module comprising:
a pair of separable contacts comprising at least one movable contact;
a movable rod securedly affixed to the movable contact;
a transmission lever pivoting around a second geometric axis parallel to the first geometric axis, said second geometric axis being common to all the breaking modules and fixed with respect to the support;
means for connecting the transmission lever to said rod;
comprising in addition a single connecting rod connecting the pole shaft to the transmission levers of the different breaking modules, the connecting rod being articulated on the one hand on at least two coaxial cranks of the pole shaft, defining a third geometric axis of pivoting parallel to the first geometric axis, and on the other hand on pivots ensuring pivoting of each transmission lever with respect to the connecting rod around a fourth geometric axis of pivoting parallel to the first geometric axis and common to all the breaking modules.
According to one embodiment, the movable rod is, in each module, connected to the connecting rod by means of a link pivoting around a fifth geometric axis parallel to the first geometric axis. A simple and advantageous geometric arrangement is thus obtained, ensuring a geometric transmission to a pole shaft situated at the height of the vacuum cartridges, while enabling the connecting rod to work in traction when closing of the contacts takes place. Preferably, the movable rod is connected to the connecting rod, in each module, by means of a link pivoting around a fifth geometric axis. The lever effect in this configuration enables the amplitude of the movement transmitted to be reduced and the forces to be geared down, which is particularly favorable when the contacts only have a small opening and closing travel, as is the case in particular for vacuum cartridges.
Preferably, the connecting rod is arranged to be under tension when closing takes place. Closing is the sequence of movement where the forces transmitted by the connecting rod are the greatest. By making the connecting rod work in tension in this sequence, the strains on the connecting rod are limited. When opening takes place, the connecting rod is under compression but the forces are relatively lower, so that the risks of deformation of the connecting rod out of its plane by buckling are avoided.
Preferably, the connecting rod comprises a metal plate shaped in such a way that its quadratic moment with respect to an axis perpendicular to a plane containing the third and fourth axes is high. The strength of the connecting rod in flexion in a plane containing the third and fourth axes enables any risk of delay on opening or closing of one of the pairs of contacts to be avoided.
According to a preferred embodiment, the connecting rod comprises a metal plate comprising two V-shaped arms, each V-shaped arm comprising a convergent end supporting a bearing for articulation with one of the cranks of the pole shaft, and a divergent end, the divergent ends of the two V-shaped arms being connected to one another by a base supporting bearings for articulation with the levers of the breaking modules.
According to one embodiment, the means for connecting the transmission lever to said movable rod comprise an insulating arm. This arrangement ensures insulation between the contacts and the mechanism which is accessible to operators.
According to one embodiment, the means for connecting the transmission lever to said movable rod comprise:
a contact pressure spring having two ends;
a first support means of a first end of the spring, securedly affixed to the lever;
a second support means of a second end of the spring, securedly affixed to the movable rod;
a mechanical connection between the first support means and the lever, performing full transmission of the movement of the lever in the closing direction and not performing transmission of the movement in the opening direction.
Preferably, each breaking module comprises a frame equipped with support bearings enabling pivoting of the transmission lever around the second axis of pivoting. The breaking modules can then be pre-assembled and tested in the plant before being assembled with the mechanism and connecting rod. This contributes to improving delayed differentiation.
Preferably, the connecting rod makes an angle close to a right angle with the transmission levers, and the movable rods work in translation in a plane appreciably parallel to the connecting rod. In other words, the geometric plane defined by the second and fourth geometric axes on the one hand and the geometric plane defined by the third and fourth geometric axes on the other hand make an angle of close to 90xc2x0 between them, whereas the movable rod is parallel to the plane containing the third and fourth axes.
The invention is particularly well suited to a configuration wherein each breaking module comprises a vacuum cartridge forming an enclosure housing the separable contacts. However, it could be adapted to other breaking principles, provided that the opening and closing travel of the contacts is small.